Manufacture of aluminates.



No. 891,677. I PATENTED JUNE 23, 1908.

0. DIBFFENBAGH. MANUFACTURE OF ALUMINATES.

APPLICATION FILED JUNE 30. 1906.

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P rrier OTTO DIEFFENBAGH, OF GRIES HEIM, GERMANY, ASSIGNOR TO QHEMISCHE FABRIK GBIESHEIM ELECTRON, OF FRANKFORT-ON-THE-MAIH, GERMANY.

MANUFACTURE OF ALUMINATES.

nates, of which the following is a specifica- 1! tion.

In the manufacture of a'luminates two inlo dustrial processes are generally adopted according to the older of which-bauxite and soda are mixed together and calcined in a reverberatory furnace at a White heat for from two to three hours, or, according to some authorities for from four to five hours,

1.2 molecule of Na,@ being used for each molecule of A1 0 and Fe O (see Dammers Technologie, Vol. I, page 622 and Jurisch Chem. Ind. 94 page 90). According to the other, and more recent, process (see German Patent No. 65,604, an addition to German Patent No. 43977) the bauxite is decomposed while, being stirred, in a boiler under a pressure of from three, to four, atmospheres (or from five, to seven, atmos heres accord- .ing tosome authorities), Wit caustic soda I lye of a specific gravity of 1.45 the time taken beingfrom two, to three, hours, the proportion ofNa Q being, for this operation, from 1.7-5 to 1.85 molecules to eachmoleculeof A1 0 heat being Tap lied by steam (see Borchers Elektrometal urgie 1903p. 151 and allowed to run into the first vessel as will Winteler: Die Aluminiuwlmdustme page 28).

t It is obvious that the older process of manufacture of aluminates in a reverberatory furnace is not economical on. account of r the large consumption of fuel. The second and more recent process, in which bauxite it is necessary to use a considerable excess of alkali and it' is most'difficult, "if not-im possible, to keep a boiler, provided with a .stirring mechanism, tight under pressure when caustic soda lye is employed. Moreover the strong corrosion to which the'ves-.

sels under ressureare exposed through the action of the caustic soda lye is a constant source of danger. X l

All the disadvantages attendant upon renderingthe bauxite soluble, by the processes hitherto known, are entirely avoided.

by the process according to this invention, which consists in. rendering soluble alumi- '55 niferous material (such for instance'as baux Specification of Letters Patent.

application filedl June 30, 1906. Serial No. 324,265;

Patented June 23. 1908 from 180 to 500 centigrade.

trated in vertical cross section means by which the process may be carried out.

In said drawing, a is a delivery pipe for lyes connected to a storage vessel not shown.

I) is the heating vessel for the lyes.

c is the delivery tube through which the. heated lyes are led from the vessel?) to the vessel d.

d is the stirring vessel in which the aluminiferous material is rendered soluble.

e represents a mechanical stirrer, andf is a fire lace, the products of combustion being led st tothe vessel (1, and the waste products of combustion passing on to heat the vessel 6 and thence out by the flue indicated.

The process according to this invention niferous material, which I will presume is bauxite, is heated to a temperature of from 180, to 200, centigrade in a vessel exposed to the direct action of fire and preferably prothe mass can be done by hand, or mechanically as may be most convenient. Next to, and above, this first vessel, is another vessel heated bythe gases from the first vessel and servilllg ess. rom this second vessel as much lye is form, with the bauxite, a stiff pulp. The temperature in the first vessel, of course, decreases to the boiling point of the added lye.

bauxite and lye has again risen to about 180 centigrade. Then a further quantity of lye is added which again causes lowering of the temperature and then the fire is again urged, and so on, until the required amount of lye .is rendered soluble by means of caustic potash lye, the contents of the vessel are heated further for from half an hour to one hour at atemperatureof from 180 to 200 centigrade.

cause if the Whole of the lye required for rendering the material soluble were introduced at once "the evaporation, occurring at 180 to 200 centigrade, would cause such excessive foaming of the mass that it would ite)=by'1neans of caustic alkali at atmospheric pressure and at a temperature ranging In the accompanying drawing 1 have illus- The lye is added in successive portions be r can be carried out as follows: The alumivided with a stirring device but the mixing of p to pre-heat the lye used in'the proc- The fireis urged and evaporation is carried f on until. the temperature of the mixture of r is decomposed in a boiler under pressure by 40 means-of alkali lye, has also its drawbacksas has been added. Then, when the material ite must either be raising steam boil over the edge of the vessel and, as heating to the aforesaid temperatures is an essential condition for'rendering the bauxite erfectly soluble, the addition of pre-heate lye in successive quantities is resorted to and thereby the excessive foaming of "the contents of the boiler is avoided.

The. method of rendering bauxite soluble when either caustic potash lye, or caustic soda lye, is used is the same, except that, in order to. obtain perfect solubility with caustic soda lye, the tempe'ratureshould be raised to from 350 to 500 centigrade after the whole of the lye has been introduced, Whereas when caustic potash lye is used, a temperature of from 180 to 200 centigrade will suflice to render bauxite completely soluble.

The necessity of employing a temperature higher than that required by the pressure process, is ractically compensated for by the direct e heat being used the cost of being thus saved.

It has been attempted to render bauxite soluble b boiling it with caustic soda lye as explaine for instance, in the J ahresbem'chten der C'hem. Technologie of Dr. J. R. Wagner 8th yearly volume for 1862 page 308 and the specification of the German Patent N 0. 67504. I The solubility produced in this manner is however imperfect, the said specification prescribing as a remedy against t is a fresh treatment of the residue by means of soda.

Aluminates have been produced by fusing together aluminium oxid and caustic potash (see Dammers Handbuch der Anorgan. Uhemie Vol. III, page 11), but hitherto no such erfect solubility of aluminiferous minera s has been obtained at atmospheric pressure with so small an amount of alkali. (Al O :Na O= 111.3) as is the case in accordance with this invention. 7

It has hitherto been presumed that bauxopened out by means of alkali lyes under pressure, or that the mixture of bauxite with caustic alkali must be Well and thoroughly calcined in order to secure satisfactory solubility (see the statement of Bayers upon the subject in the specification of German Patent N 0. 439772.

or calcination process, as in addition to excessive fuel consumption, the disadvantage that it cannot owin to the high temperature required, be carrierI out in iron vessels: and that stoneware is decomposed by glowing caustic alkali and aluminate, and thus rapidly destroyed.

The present process of rendering soluble aluminlferous material such as bauxite, at a tern erature of from 180 to 500 centigra e by means of caustic alkali has thereore the important advantages that in addi- 1 tion to possessing all the a vantages which renderin bauxite soluble under pressure by means 0 alkali lye presents over the older process in a reverberatory furnace by means of soda, or other caustic alkali, that it can be carried out in iron vessels, and is entirely free from danger and requires less al kali than does theprocess under pressure and therefore the preci itation of the alumina from the alummate ye can be efiected more rapildly and more thoroughly than hitherto.

aim: 1

The herein described process of manufacturing aluminates, which consists .in stirring separately aluminiferous heating it to a temperature of 180 to 500 material while centigrade at atmospheric pressure, intro- 'ducing into the stirred mass first as much caustic alkali as will form with the aluminiferous material astiff pulp, raising again the temperature of the mass to 180 to 500 centl rade, then adding a further quantity of al ali, raisin again the temperature to 180 to 500 centigrade and so on until the re uired amount of caustic lye has been adiled, continuing the heating of the mass for some time, lix iviating the molten mass and filtering off the alummate solution ,thus obtained, as and for the pur ose set forth.

In testimony whereof I ave signed my name to" this specification in the presence of two subscribing witnesses.

OTTO DIEFFENBAOH. Witnesses:

FRANZ HASSLAOHER, ERWIN DIPPEL. 

